The present invention relates to the field of internal combustion engines and more specifically relates to mechanisms used to split the operation of an internal combustion engine, so that it has the capability to alternately operate one-half or all of its cylinders.
It has long been known that internal combustion engine efficiency is greatest when cylinders were operating under relatively high loads. However, the normal operating conditions of, for instance, a typical automobile engine do not place the requisite high levels on the cylinders, resulting in uneconomical fuel consumption a great percentage of the operating time. The efficiency of the engine is directly related to the amount of air being compressed to produce the power output of the engine, since maximum air is applied to the cylinders when the throttle is open for high loads. Given the fact that cylinder load increases compression pressures which increase the engine's efficiency, the advantage of having a split engine becomes apparent by imparting high loads to half the cylinders during normal operating conditions.
Included in the design of a split engine modification is the ability to utilize all the cylinders when the engine experiences heavier loads or higher performance requirements. This provides the operator of the split engine the advantages of good fuel economy under normal operating conditions and reserve power when needed.
One area of concern, however, in operating a split engine is that the same group of cylinders always remain the active cylinders, experiencing the most wear while the remaining group of cylinders experience relatively small amount of wear and fatigue. Consequently, the engine life will be dependent upon the life of the first or active group of cylinders even though the second or inactive group of cylinders have a longer life.
Another area of concern in obtaining optimum efficiency with a split engine design has been the possible drag forces caused by the inactive pistons being turned within their cylinders by the engine crankshaft. The energy needed to turn these inactive pistons is a power drain on the active pistons, decreasing fuel economy.